A transient voltage suppressor, or TVS, is a device that is employed to reduce the effects of temporary overvoltage conditions in an electronic circuit. For example, some TVS devices attenuate voltage spikes, while other TVS devices are designed to divert excessive voltages to ground. A common device used for transient voltage suppression is a transient voltage suppression diode, which is typically used for unidirectional or bidirectional electrostatic discharge protection of transmission or data lines in electronic circuits. TVS devices can also be used to protect against overvoltages being applied to the gate of a power MOSFET. An overvoltage on the gate of a MOSFET can damage or destroy the gate dielectric of the MOSFET, potentially leading to device failure. A transient voltage suppression diode may be implemented simply using a Zener diode placed in parallel with a load that is to be protected.
A unidirectional TVS protects against overvoltages having a single (positive or negative) polarity, while a bidirectional TVS protects against overvoltages having positive and/or negative polarity.
Silicon carbide has been proposed as a possible material for transient voltage suppressors for low voltage applications, such as protection of low voltage power lines. See, e.g., K. V. Vassilevski, et al., “Low Voltage Silicon Carbide Zener Diode,” Materials Science Forum, vols. 457-460, pp. 1029-1032 (2004). However, as noted therein, at voltages below 50 V, the advantages of silicon carbide may be overshadowed by high contact and substrate resistivities. Furthermore, the Zener diodes described in Vassilevski had a positive breakdown voltage temperature coefficient and were described as having mixed. Zener and avalanche breakdown characteristics.